Compositions And Methods For Controlled Break Of Fluid-Loss Barriers Post-Perforation

ABSTRACT

Embodiments of the disclosure are materials, methods, and tools to make and break fluid loss control barriers within the perforations of a wellbore on-demand. Tools include heat emitting tools, magnetic tools, acoustic tools, gamma ray tools, and vacuum tools.

PRIORITY CLAIM

The present application claims priority to U.S. Provisional Patent Application No. 62/436,110, filed Dec. 19, 2016, and titled “Compositions and Methods for Controlled Break of Fluid-Loss Barriers Post-Perforation.” The entire contents of the foregoing application are hereby incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to tools, compositions and methods for creating and breaking fluid-loss barriers, and more specifically to tools, compositions and methods that can be deployed to achieve on-demand removal of perforation-filling material.

BACKGROUND

In connection with completing a well for extracting a natural resource such as natural gas or petroleum, the well casing and the cement on the exterior of the wellbore must be perforated at production depth to allow movement of fluid into and/or out of the wellbore. Perforation is done after the well is fully cemented and the cement has dried. These perforations are used to provide a pathway for fluid to flow between the formation and the well to allow production of hydrocarbons, for example. However, for cased and perforated completions, materials and debris that fill or plug perforations are a common restriction to productivity, as they disrupt the flow of fluid or gas. The material in perforations may comprise solid debris from the perforation gun used to create the perforation; or it may comprise material, which can be referred to as fluid loss control (FLC) pills or barriers, intentionally placed into the perforations to arrest fluid-loss prior to installation of the lower completion. Current methods for cleanup of perforations are highly inefficient, commonly involving bullheading of acids from the surface to clean up the components of the perforation material that are both acid soluble and are accessible during injection. However, not all materials lodged in perforations are acid soluble. Further, across many long perforated intervals, it is common for the perforation cleaning treatment to preferentially only clean the perforations that lie along the direction of maximum horizontal stress, along which a fracture will propagate. In cases of low rate acid injection to clean perforations, the acid may preferentially leakoff into perforations across high-permeability streaks, leaving large intervals understimulated due to perforations that are still plugged. Several degradable FLC barrier materials have been proposed; but their utilization has been limited as their degradation is often limited to a narrow range of downhole temperatures and fluid environments.

Currently, no downhole solution exists that can provide true on-demand breaking of fluid-loss barriers that will uniformly clean all perforations. Disclosed herein are ways in which perforation FLC barriers can be removed or degraded on-demand. Embodiments of different tools, materials, and methods are disclosed below.

SUMMARY OF THE INVENTION

A general embodiment of the disclosure is a method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well, comprising, perforating a wellbore, forming, within the perforation, a fluid loss control barrier comprising heat susceptible material; inserting a heat emitting tool comprising a heater into the wellbore, and applying heat to the perforation using the heater. In embodiments, the heater is a heat coil. In some embodiments, the heat susceptible barrier comprises wax. In other embodiments, the heat susceptible barrier comprises an emulsion, such as an oil/water emulsion. In some embodiments, the heat emitting tool further comprises a power source, such as a battery. In specific embodiments, the heat emitting tool further comprises a sand screen located above the heater, a lower completion, or a wash pipe located above the heater. In some embodiments, the heat from the heater penetrates less than 5 feet, less than 4 feet, less than 3 feet, less than 2 feet, less than 1.5 feet, less than 1 foot, or less than 7 inches into the formation from the exterior of the wellbore and/or the heat from the heater penetrates at least 6 inches, 9 inches, 1 foot, 1.5 feet, or 2 feet into the formation from the wellbore. In another embodiment, the heat emitting tool is embedded in a sand screen. In some embodiments, applying heat to the wellbore perforations using the heater happens at least partially concurrently with installing the lower completion or after installing the lower completion.

Another general embodiment is an on-demand method for making and removing fluid-loss barriers from perforations connecting a well with a formation comprising perforating cement and casing located between the well and the formation, creating a fluid loss control barrier comprising fluid loss control material within the perforations, thereby plugging the perforations such that fluid cannot move between the interior of the well and the formation, and lowering a perforation fluid loss barrier breaking tool into the well past the perforations, thereby breaking the fluid loss control barrier and allowing fluid movement between the interior of the well and the formation. In embodiments, the perforation fluid loss barrier breaking tool physically removes the fluid loss control material from the fluid loss control barrier. In other embodiments, the perforation fluid loss barrier breaking tool degrades the fluid loss control material from the fluid loss control barrier. In some embodiments, the fluid loss control barrier comprises microwave susceptible particles and the perforation fluid loss barrier breaking tool comprises a microwave generator; the fluid loss control barrier comprises gamma ray susceptible particles and the perforation fluid loss barrier breaking tool comprises a gamma ray generator; the fluid loss control barrier comprises acoustic susceptible particles and the perforation fluid loss barrier breaking tool comprises an acoustic force generator; or the perforation fluid loss barrier breaking tool is attached to a wash-pipe. In specific embodiments, the perforation fluid loss barrier breaking tool is attached to a lower completion, a wash-pipe, or is embedded in a sand screen. In some embodiments, breaking the fluid loss control barrier happens at least partially concurrently with installing the lower completion or after installing the lower completion.

Another general embodiment is a method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well, comprising, perforating a wellbore, forming, within the perforation, a fluid loss control barrier comprising acoustic susceptible material, inserting an acoustic emitting tool comprising an acoustic generator into the wellbore, and applying acoustic force to the perforations using the acoustic generator. In some embodiments, the acoustic susceptible barrier comprises acoustic susceptible material dispersed within a viscous phase. In some embodiments, the acoustic susceptible barrier comprises acoustic susceptible bridging agent such as silica spheres. In specific embodiments the acoustic susceptible barrier comprises an emulsion, such as an oil/water emulsion. In some embodiments, the acoustic emitting tool further comprises a power source, such as a battery or a generator. In some embodiments, the acoustic emitting tool further comprises a sand screen located above the acoustic generator. In some embodiments, the acoustic force penetrates at least 6 inches, 9 inches, 1 foot, 1.5 feet, or 2 feet into the formation from the wellbore. In some embodiments, the acoustic emitting tool is attached to a wireline, a wash-pipe, or a lower completion. In some embodiments, applying acoustic force to the perforations using the acoustic generator happens at least partially concurrently with installing the lower completion or after installing the lower completion.

Another general embodiment of the disclosure is a method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well, comprising, perforating a wellbore, forming, within the perforation, a fluid loss control barrier comprising gamma ray susceptible material, inserting a gamma ray emitting tool comprising a gamma ray source into the wellbore, and applying a gamma ray to the perforation using the gamma ray generator. In some embodiments, the gamma ray susceptible barrier comprises gamma ray susceptible material dispersed or dissolved with a viscous phase. In specific embodiments, the gamma ray susceptible barrier comprises a gamma ray susceptible chemical, wherein when exposed to a gamma ray the chemical generates reactive intermediates, such as free radicals, acids, oxidizers, or mixtures thereof. In some embodiments, the gamma ray susceptible barrier comprises one or more of starch, xanthan, guar, and calcium carbonate which reacts with the reactive intermediate. In specific embodiments, the gamma ray emitting tool further comprises a power source, such as a battery or a generator. In other embodiments, the gamma ray emitting tool is powered from the surface. In some embodiments, the gamma ray emitting tool further comprises a screen located above the gamma ray generator. In specific embodiments, the gamma rays penetrate less than 5 feet, less than 4 feet, less than 3 feet, less than 2 feet, less than 1.5 feet, less than 1 foot, or less than 7 inches into the formation from the wellbore and/or the gamma rays penetrate at least 6 inches, 9 inches, 1 foot, 1.5 feet, or 2 feet into the formation from the wellbore. In some embodiments, the gamma ray emitting tool is attached to a wireline, the lower completion, or a wash-pipe. In some embodiments, applying a gamma ray to the perforation using the gamma ray generator happens at least partially concurrently with installing the lower completion or after installing the lower completion.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate only example embodiments of methods, systems, and devices for creating and removing fluid loss barriers from perforations and are therefore not to be considered limiting of the scope of the disclosure. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.

FIGS. 1a-c illustrate the method of two types of perforation FLC barrier breaking tools.

FIG. 2 illustrates a perforation FLC barrier breaking tool suspended within a well.

FIG. 3 illustrates an embodiment of a heat emitting perforation FLC barrier breaking tool.

FIG. 4 illustrates a method of making and breaking, on-demand, a perforation FLC barrier.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The example embodiments discussed herein are directed to systems, apparatuses, and methods of cleaning perforations within a well casing and cement. Specific embodiments include systems, apparatuses, and methods of removing or degrading FLC materials within wellbore perforations.

Example embodiments will be described more fully hereinafter, in which example embodiments of systems, apparatuses, and methods of cleaning perforations within a wellbore are described. It should be understood that such systems, apparatuses, and methods may be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the claims to those of ordinary skill in the art. Like, but not necessarily the same, elements in the various figures are denoted by like reference numerals for consistency.

“Near wellbore” as used herein, refers to within 1 foot, 10 inches, 8 inches, or 7 inches of any exterior point of the wellbore.

“Perforation FLC barrier breaking tool” or “tool” as used herein, refers to a tool of the disclosure that removes or degrades the FLC barrier located within a perforation, thereby unplugging the perforation, on demand, and allowing for the flow of fluid between the formation and the well. That is, the tool is able to break a FLC barrier allowing the flow of fluid across the barrier. The tool may fully remove the barrier, or may just degrade the barrier in situ such that fluid is able to move across the broken barrier.

“FLC barrier” or “perforation FLC barrier,” as used herein, refers to a FLC barrier located within a perforation which has active fluid containment. That is, the FLC barrier does not allow fluid flow between the well and the formation. “FLC material,” as used herein, refers to any type of FLC material which is in, or can be used to form, a FLC barrier. FLC material can be solid and/or fluid. In some embodiments, “FLC material” may refer to a bridging agent comprising solid material, optionally also referring to its carrier fluid which is often viscosified. In other embodiments, a FLC material may comprise a viscosified fluid that does not contain solid bridging agents; certain embodiments may include emulsions, crosslinked fluids, and other high-viscosity fluids.

“Breaking” the perforation FLC barrier refers herein to degrading the integrity of the FLC barrier or removing the FLC barrier, thereby allowing the flow of fluid through the perforations between the formation and the wellbore.

FIGS. 1a-c illustrate two methods through which two general types of perforation FLC barrier breaking tools can function. Only one side of the wellbore is illustrated. The specifics of each type of tool are described in more detail below. The tool 1, is lowered past perforations 2 running through the cement 3 and casing (not shown). The perforations 2 contain a FLC material 4. The FLC material 4 creates a FLC barrier between the formation 5 and the interior of the well 6 such that fluid is not able to flow between the interior of the well 6 and the formation 5 (FIG. 1a ). The first type of tool 1, shown in FIG. 1b , physically removes FLC material 4 from the perforations 2, breaking the FLC barrier and thereby restoring fluid flow between the interior of the well 6 and the formation 5. The removed FLC material 7 is shown attached to the tool 1. A second type of tool 1, shown in FIG. 1c , degrades or breaks the FLC material 4 such that the integrity of the FLC barrier is broken and fluid flow is restored between the interior of the well 6 and the formation 5. The degraded FLC material 8 is shown in FIG. 1c . Both types of tools and methods are able to break a FLC barrier on demand.

The first type of perforation FLC barrier breaking tool described above uses tools with sufficient force to pull FLC material from inside perforations into the wellbore, thereby breaking the FLC barrier (FIG. 1b ). In certain example embodiments, a tool is inserted into the wellbore after perforation and after the perforation barriers have been formed; the tool could be inserted while inserting the lower completion, such as having the tool attached to the bottom of the lower completion, or the tool could be deployed on a wireline trip whose partial objective was breaking the FLC barrier, for example. In an example embodiment, once the tool reaches the desired depth of the first exposed perforations, a signal would be applied from the surface to activate the downhole tool to act to pull or otherwise dislodge solid FLC material from the FLC barrier and/or perforation debris from within the perforations. Once the initial perforation FLC material is pulled into the wellbore, the tool could be moved downhole and allowed to continue to remove perforation FLC material from subsequent perforations downhole across from which the tool passes. Specific embodiments of disclosed tools which can physically remove FLC material from the perforations are further described below. In another example embodiment, the tool could be inserted into a cased and perforated wellbore which lacked sand control screens only after installation of the upper completion. In such a cased and perforated completion, the perforation event may happen before the installation of the upper completion and the FLC material could provide fluid-loss control during the installation of the upper completion. After upper completion installation, the tools would be subsequently deployed to remove perforation FLC material from the perforations.

The second type of perforation FLC barrier breaking tool disclosed above uses tools that apply force to activate (such as through a reaction within the FLC-packed perforation), degrade, and/or dissolve solid perforation filling material on-demand (FIG. 1c ). Again, methods for deployment could include deployment on wireline trip to clean out perforations; or alternative methods could include assembly of the preferred tools onto the end of a lower completion and either leaving the tool downhole (in appropriately sized rat-hole), making the tool out of degradable solids that will degrade downhole with time, or making the tool removable on washpipe.

Magnetic Tool, Magnetic FLC Material, and Methods of Using the Combination

Embodiments of the first type of perforation FLC barrier breaking tool disclosed include tools which apply magnetic force to dislodge and remove magnetically-attractive debris and magnetically-attractive FLC material from a perforation. This may more specifically include electromagnetic tools which are powered, such as an electromagnet. The electromagnet may be powered from the surface, from a localized generator, or from a stored power source, such as a downhole battery. The magnetic tool is used with a FLC barrier that is susceptible to magnetic fields. As used herein, a “magnetic susceptible FLC barrier” refers to a FLC barrier which comprises magnetically active material which, when removed, disrupts the integrity of the FLC barrier. The magnetic susceptible FLC barrier comprises magnetic susceptible FLC material, which may include magnetic susceptible solid material acting as a bridging agent in the FLC material-filled perforation. In some embodiments, the magnetic field of the magnetic tool extends less than 2 feet, less than 1 foot, or less than 8 inches from the magnetic tool.

Some embodiments of the tool include centralizers, which are configured to ensure the magnetic/electromagnet tool does not stick to one side of the casing and instead remains centralized relative to perforations of similar depth. Such centralizers can include mechanical centralizers, such as bow spring centralizers.

Embodiments of the disclosure include a magnetic susceptible FLC material which comprises magnetically active materials such as ferromagnetic materials. The FLC material may include suspended particles comprising metals and/or alloys where those particles are used as bridging agents. Specific embodiments include one or more of iron, nickel, cobalt, steel and the like. These materials may also include various metal oxides such as Fe₂O₃, FeOFe₂O₃, CuOFe₂O₃, MgOFe₂O₃, and others.

Magnetic susceptible FLC material may be deployed from the perforation gun and/or a debris orb. Magnetic susceptible FLC material may also be deployed through suspension within a fluid loss control pill which is pumped into the perforations from the surface after the perforations are created in order to create a FLC barrier.

Magnetic susceptible FLC material may be suspended in a base fluid, such as a viscous aqueous base fluid to compose a fluid loss control pill. Aqueous base fluids may include brine solutions of sodium chloride, potassium chloride, calcium chloride, calcium bromide, zinc chloride, zinc bromide, potassium formate, and mixtures thereof to achieve a target density. These carrier fluids may be further viscosified. In some embodiments, the magnetic susceptible FLC material is suspended in a fluid that is then diluted prior to entering the wellbore. In some embodiments of the disclosure, the fluid loss control pill is in the area of the perforation gun prior to forming the perforations, allowing it to immediately leakoff into perforation tunnels after the perforation event.

In some embodiments of the disclosure, the magnetic susceptible FLC material is substantially circular. In other embodiments, the material may be irregular or non-spherical. In certain embodiments, mixtures of circular and non-circular materials are used. In embodiments of the disclosure, the magnetic susceptible FLC material is less than 200 microns long in the largest dimension. In specific embodiments, magnetic susceptible FLC material is less than 200, 175, 150, 125, 100, 90, 80, 70, 60, 50, or 25 microns long in the largest dimension. In embodiments of the disclosure, the magnetic particles in the magnetic susceptible FLC material comprise a mixture of different sized magnetic particles, wherein the longest dimension of the largest particle is less than 200 microns. The size and mixture of sizes of the magnetic particles may be designed specific to the reservoir properties, such as permeability or average pore-throat size. The magnetic particle sizes can be designed towards the permeability of the near wellbore region of the formation.

In some embodiments the magnetic susceptible FLC material may comprise a solid-stabilized emulsion, such as a nanoparticle-stabilized emulsion where the nanoparticles are magnetically active (such as Fe₂O₃ nanoparticles, or the like). In a specific embodiment, the perforation event may occur with a wellbore full of this emulsion comprising magnetic FLC materials that will then undergo leakoff into the perforations following the actual perforation of the walls of the wellbore. In these methods, a magnetic tool, as described above, will enter the wellbore as desired and applies magnetic force that removes the nanoparticles from inside the perforation; this action destabilizes the emulsion (in some embodiments causing phase-separation), which lowers the overall viscosity and lowers the ability to maintain fluid loss control. The net result is improved cleanup of emulsion (such as a magnetic mud) that fills the perforations.

There are several methods for deploying the magnetic perforation FLC breaking tools. Embodiments of the disclosure include deployment via wireline, for example, during a trip past the perforations prior to installation of the lower completion. The magnetically active tool could also be attached to the bottom of the lower completion (i.e., bull-nose) during installation. The lower completion would be conveyed slowly past the perforations, dislodging magnetically active FLC material within a FLC barrier. In some embodiments, the electromagnet is turned off between areas of perforations, allowing the magnetic FLC material already attracted to the magnet to fall to the bottom of the well. The magnetic perforation FLC breaking tool could also be installed in or on a sand screen. In other embodiments, the magnetic perforation FLC breaking tool could be deployed attached to a wash pipe.

Localized Vacuum Tool and Methods of Use

In some embodiments, a localized pulse of vacuum is applied to an isolated area of perforations. In specific embodiments, the vacuum tool comprises one or a series of vacuum chambers similar to “sand bailers.” In embodiments, the vacuum tool comprises a mechanism to receive an external signal to open or close the canister, thereby activating the vacuum tool. In embodiments, the vacuum tool comprises packers, such as straddle packers, to localize the vacuum action to a specific area of the wellbore, such as an area which contains plugged perforations.

The vacuum tool could be deployed via wireline and could be used to remove FLC barriers prior to installing the completion. The vacuum tool could also be attached to the bottom of the lower completion (i.e., bull-nose) during installation. With external power to activate the vacuum canister, the lower completion could be run slowly past the perforations, dislodging FLC material.

Microwave Emitting Tool and Methods of Use

The second type of perforation FLC breaking tools described above include downhole tools designed to emit local energy radially in the direction of the perforations. In the current embodiments, a microwave emitting tool is used to break a FLC barrier that is susceptible to microwave radiation. That is, when the microwave-susceptible FLC barrier is subjected to microwaves, it degrades, breaking the FLC barrier and allowing fluid to flow through the perforations. The microwave susceptible barrier comprises microwave susceptible material. In embodiments of the disclosure, the microwave radiation extends only in the near wellbore region of the area of perforations. In some embodiments, the microwave radiation extends less than 2 feet, less than 1 foot, less than 10 inches, less than 8 inches, less than 7 inches from the tool. In embodiments, the microwave radiation extends at least 4 feet, at least 3 feet, at least 2 feet, at least 1 foot, or at least 6 inches from the tool.

Embodiments of the blended pills includes microwave susceptible FLC materials blended into a fluid which comprises a viscosifier which comprises microwave susceptible material and/or a bridging agent which is microwave susceptible. Such microwave susceptible materials lose their solid character during microwave heating, such as wax beads or core-shell capsules (micron sized or nano-sized) that would degrade upon microwave power due to the core material being preferentially susceptible to microwave radiation. In one embodiment, the shell of the core-shell capsule comprises wax and the core comprises water. In other embodiments, plastic materials with a low melting point could be used in place of the wax material; examples could include polycaprolactone and other plastics with low melting-point. In some embodiments, the melting temperature of the microwave susceptible material is above the reservoir temperature. In some embodiments of the disclosure, the individual microwave susceptible materials largest dimension is less than 200 micrometers.

In some embodiments, the microwave susceptible FLC material is a viscous solution of emulsion. For example, the microwave susceptible material is a viscous oil/water emulsion. The oil could be an immiscible oil, for example. The water could be a water-based phase, including brines and fresh water, for example. When subjected to the microwave tool, the oil/water emulsion within a microwave susceptible barrier breaks down due to the preferential heating of the aqueous phase, which causes the emulsion to lose viscosity and breaks a FLC barrier comprising the microwave susceptible emulsion.

Heat Emitting Tools and Methods of Use

The second type of perforation FLC barrier breaking tools include downhole tools designed to emit sufficient heat that will melt heat susceptible FLC material within the FLC barrier. The heat emitting tool could comprise a heating-coil, for example. The heat emitting tool would emit heat radially from the tool into the near well bore region. The heat emitting tool acts on FLC materials that are degradable with application of local heating. In embodiments, the heat emitting tool is suspended beneath a wireline tool. The heat susceptible FLC material can include wax, polymer, metals, alloys and similar solids known to melt at known temperatures. In embodiments, the heat susceptible FLC material melts at a temperature higher than the temperature of the formation. The heat emitting could be lowered past heat susceptible FLC barriers in perforations slowly, in order for the formation around the perforation to heat to a sufficient temperature to degrade the heat susceptible FLC barrier comprising heat susceptible FLC material.

In embodiments of the disclosure, the heat emitting tool emits heat greater than the temperature of the formation at least 2 feet from the tool, at least 1.5 feet from the tool, or at least 1 foot from the tool.

In embodiments of the current disclosure, the heat-emitting tool would raise the temperature of the perforation-filling fluid/solid mixture to the target melt temperature of the specific solid FLC material. This temperature could be greater than 100° F., 125° F., 150° F., 180° F., 200° F., 220° F., 250° F., 275° F., 300° F., 325° F., 350° F., for example.

In some embodiments, the heat susceptible FLC material is a wax, such as a polyether wax, microcrystalline wax, montanic acid/ester wax, ethylene copolymer wax, synthetic wax, natural wax, polyethylene wax, micronized polyethylene, hi-melt crystalline polyethylene, polyolefin wax polymer, polypropylene, or any mixtures thereof. In some embodiments, the heat susceptible FLC material is in pellet, and/or granule form. In additional embodiments, the heat susceptible FLC material has a melting point of between 116-350, for example between 115-175, 116-124, 130-150, 150-170, 170-185, 170-190, 175-225, 180-200, 190-200, 190-210, 210-225, 210-230, 215-250, 225-250, 225-275, 235-245, 250-260, 270-290, 275-325, 300-350, 315-340° F. In some embodiments, the heat susceptible FLC material particle size is between 5-100 microns. For example, the particle size could be 6-8, 7-10, 20-26, about 5, about 6, about 7, about 8, about 9, about 10, 4-10, 5-12, 6-8, 11-15, 16-25, 25-35, 35-45, 45-55, 55-65, 65-75, 75-85, 85-95, 90-100 microns.

Acoustic Tool and Methods of Use

The second type of perforation FLC barrier breaking tool described above includes downhole tools designed to emit acoustic force. The acoustic tool could be used with two types of FLC materials. The first type of FLC material includes solid bridging agents that are susceptible to acoustic force. That is, the bridging agent may shatter or disintegrate once subjected to acoustic force. Examples of acoustic susceptible bridging agents are brittle capsules that shatter with sufficient applied acoustic force, such as silica spheres, core-shell capsules with thin plastic coatings, and similar materials.

The second type of acoustic susceptible FLC material is a FLC material composed of one or more fluid types, such as an emulsion. The fluid types, mixed together, form a FLC barrier capable of controlling fluid loss. The application of an acoustic signal or harmonic signal causes the immiscible fluid phases to separate, thus causing a FLC barrier comprising the acoustic susceptible FLC material to lose integrity.

Gamma Ray Tool and Methods of Use

The second type of perforation FLC barrier breaking tool described above also includes downhole tools designed to emit gamma rays. The gamma ray emitting tool applies gamma rays to induce chemical change and/or activation of a FLC material within the perforation FLC barrier. Gamma rays induce many chemical changes, such as formation of peroxide (oxidizer), formation of acid, and degradation of polymers.

The gamma ray emitting tool may be matched with a material, such as a FLC material which comprises polysaccharide polymers, such as starch, xanthan, guar, or others. These materials also include the use of FLC pills which include calcium carbonate solids, which could be removed on-demand by acids formed downhole by gamma ray radiation.

The gamma ray tool may be targeted to break down a gamma ray viscosifier and/or a bridging agent within the FLC barrier. For example, the bridging agent within the FLC barrier may be acid soluble and/or a starch which, when combined with another chemical, creates free radicals in acid, which then breaks down the solid FLC bridging material and dissolves the FLC barrier. The injected chemicals forming the FLC barrier may also comprise gamma ray susceptible material, such as a chemical that can form either an oxidizer or an acid when subjected to gamma rays. In both embodiments, the gamma ray force would initiate a primary reaction to convert inert precursor into an active chemical, such as acid or oxidizer; these activated components will then undergo the secondary reaction (i.e., acid with CaCO₃ or oxidizer with polysaccharide) to degrade the FLC action.

Examples of gamma-ray precursor chemicals which are initially inert include: free radical precursors, such as hydrogen peroxide; gamma ray susceptible FLC bridging agents such as calcium carbonate, other acid soluble solids; gamma ray susceptible FLC viscosifiers such as starch, xanthan, guar, derivatized guar, derivatized cellulose, and others.

Perforation FLC Barrier Breaking Tool Structure

While the perforation FLC breaking tools described herein function in different ways to break the FLC barrier, they may be assembled similarly. In embodiments, the tools described herein have a wireline connection, for example, threading, clips, or brackets that allow the tool to be attached to a wireline. In other embodiments of the disclosure, the tools comprise a lower completion connection, such as threading, clips, or brackets, that is configured to be attached into a lower completion pipe. In some embodiments, the tool is connected either directly or indirectly to the bottom of a lower completion. In some embodiments, the tool is connected to the washpipe. In some embodiments, the tool is connected below a lower completion, such as directly or indirectly to the bull nose of a screen. In specific embodiments, the screen is an expandable screen, a wire-wrapped screen, a premium mesh screen, an alternative woven screen, or a thru-tubing screen, for example.

In specific embodiments of the disclosure, the tool is configured to be sacrificed at the bottom of the well. For example, the tool could be partially or fully composed of degradable material.

Method of Use of Disclosed Tools

Embodiments of the perforation FLC barrier breaking tools and methods described herein have multiple mechanisms for improving clean-up of perforations. Optional embodiments include preferentially acting only to weaken (but not fully dissolve) the FLC barrier within the perforations toward subsequent cleanup operation.

Embodiments of deploying the perforation FLC barrier breaking tool to apply the required force to degrade or remove the FLC barrier may be carried out in a number of ways. In some embodiments, the tool may be deployed via wireline in a dedicated trip downhole. In other embodiments, the tool will be deployed via wireline which includes other downhole tools. In other embodiments, the tool may be deployed as part of the lower completion (disposable), or attached to the washpipe (retrievable). This will allow the action of the tool to clean up perforation damage during the running of the lower completion past the perforated interval, as the lower completion is being installed. In this embodiment, additional time may be added to the time to run in hole with the tool/completion assembly, to ensure maximum cleanup. In some embodiments, the FLC barrier breaking tool may be attached to a sand screen. For example the FLC barrier breaking tool may be imbedded in the sand screen. The completion may be designed such that the tool is disposable. That is, where it will remain a part of the lower completion or sand screen through the productive lifetime. Alternatively, that tool may fully or partially comprise degradable solid material, where after activation of the tool to clean up perforations, the tool can then remain downhole and will slowly degrade during production. Alternatively, the tool may remain downhole but will comprise a non-degradable material that will simply reside in the toe or bottom of the wellbore after action (with the wellbore length designed to accommodate storage of this sacrificial tool). Depending on how the tool is deployed, breaking the fluid loss control barrier can happen at least partially concurrently with installing the lower completion or after installing the lower completion.

In another example embodiment, the tool could be inserted into a cased and perforated wellbore which lacked sand control screens only after installation of the upper completion. In such a cased and perforated completion, the perforation event may happen before the installation of the upper completion and the FLC material could provide fluid-loss control during the installation of the upper completion. After upper completion installation, the tools would be subsequently deployed to remove perforation FLC material from the perforations.

Embodiments of the disclosure include different apparatus and methods of powering the perforation FLC barrier breaking tool. Embodiments include power applied from the surface, such as through established wireline techniques. Other embodiments include powering the tool from the surface within the lower completion. In other embodiments, the tool may be powered from a self-contained power source that will enter the wellbore with the lower completion/tool assembly during the tools installation and action. Such power sources include down hole power generators and batteries, for example.

In embodiments of the disclosure, the tool is automatically triggered, such as by reaching a specific depth. In other embodiments of the disclosure the tool is triggered from the surface, such as through signals that are transmitted through fiberoptics, through wireless means, and otherwise.

Additional Example Embodiments

FIG. 2 shows a perforated well. The perforated well includes cement 3 along the edge of the wellbore, and an interior casing 22. There is a blowout preventer 23 installed at the surface 24 of the well. Perforations 25 provide a fluidic connection between the interior of the wellbore 6 and the formation 5 through the cement 3 and casing 22. A wireline 28 is extended into the well with an perforation FLC barrier breaking tool 1 suspended from it. The tool 1 illustrated could be any disclosed herein, such as an electromagnetic tool, a microwave tool, a vacuum tool, a gamma ray tool, and acoustic tool, or a heating tool.

FIG. 3 illustrates an embodiment of a heat emitting tool 31 attached below a sand screen 32. The heat emitting tool 31 is attached to the screen through a connector 33, illustrated in FIG. 3 as a threaded connection. The heat emitting tool 31 comprises a power source 34 connected to heating coil 35. The heating coil 35 is part of the heater 37.

FIG. 4 illustrates an example method of using a tool of this disclosure during a well completion. First, shown in step 41, the well is perforated, thereby fluidly connecting the interior of the wellbore with the formation through the perforations within the cement and casing. Then the perforations are plugged with fluid loss control material, as given in step 42. After the perforations are plugged other work may be performed on the well before the perforations are unplugged. When it is time to remove plugging material from the perforations, a tool of this disclosure is then lowered into the well past the plugged perforations (step 43), at a controlled rate, thereby removing plugging material from the perforations on demand. After the perforations are unplugged fluid is able to move between the interior of the well and the formation in step 44.

Although embodiments described herein are made with reference to example embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope and spirit of this disclosure. Those skilled in the art will appreciate that the example embodiments described herein are not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the example embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments using the present disclosure will suggest themselves to practitioners of the art. Therefore, the scope of the example embodiments is not limited herein. 

What is claimed is:
 1. A method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well in a formation, comprising: perforating a wellbore to form the wellbore perforations between the wellbore and the formation; forming, within the wellbore perforations, a fluid loss control barrier comprising heat susceptible material; inserting a heat emitting tool comprising a heater into the wellbore; and applying heat to the wellbore perforations using the heater.
 2. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heater is a heat coil.
 3. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat susceptible material comprises wax.
 4. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat susceptible material comprises an emulsion.
 5. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 4, wherein the emulsion is an oil/water emulsion.
 6. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat emitting tool further comprises a power source.
 7. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 6, wherein the power source is a downhole battery.
 8. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat emitting tool further comprises a sand screen located above the heater.
 9. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat from the heater penetrates less than 5 feet, less than 4 feet, less than 3 feet, less than 2 feet, less than 1.5 feet, less than 1 foot, or less than 7 inches into the formation from the exterior of the wellbore.
 10. The method of for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat from the heater penetrates at least 6 inches, 9 inches, 1 foot, 1.5 feet, or 2 feet into the formation from the wellbore.
 11. The method of for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat emitting tool is attached to a wash-pipe.
 12. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat emitting tool is attached to a lower completion.
 13. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, wherein the heat emitting tool is embedded in a sand screen.
 14. The method of making and removing fluid-loss barriers in a wellbore perforations prior to producing a well of claim 1, wherein applying heat to the wellbore perforations using the heater happens at least partially concurrently with installing a lower completion.
 15. The method of making and removing fluid-loss barriers in a wellbore perforations prior to producing a well of claim 1, wherein applying heat to the wellbore perforations using the heater happens after installing a lower completion.
 16. The method for making and removing fluid-loss barriers in wellbore perforations prior to producing a well of claim 1, further comprising installing an upper completion prior to inserting the heat emitting tool.
 17. An on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation comprising: perforating cement and casing located between the wellbore and the formation; creating a fluid loss control barrier comprising fluid loss control material within the perforations, thereby plugging the perforations such that fluid cannot move between the interior of the well and the formation; and lowering a perforation fluid loss barrier breaking tool into the wellbore past the perforations, thereby breaking the fluid loss control barrier and allowing fluid movement between the interior of the well and the formation.
 18. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the perforation fluid loss barrier breaking tool physically removes the fluid loss control material from the fluid loss control barrier.
 19. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the perforation fluid loss barrier breaking tool degrades the fluid loss control material from the fluid loss control barrier.
 20. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the fluid loss control barrier comprises microwave susceptible particles and the perforation fluid loss barrier breaking tool comprises a microwave generator.
 21. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the fluid loss control barrier comprises heat susceptible particles and the perforation fluid loss barrier breaking tool comprises a heater.
 22. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the fluid loss control barrier comprises gamma ray susceptible particles and the perforation fluid loss barrier breaking tool comprises a gamma ray generator.
 23. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the fluid loss control barrier comprises acoustic susceptible particles and the perforation fluid loss barrier breaking tool comprises an acoustic force generator.
 24. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the perforation fluid loss barrier breaking tool is attached to a wash-pipe.
 25. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the perforation fluid loss barrier breaking tool is attached to a lower completion.
 26. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein the perforation fluid loss barrier breaking tool is embedded in a sand screen.
 27. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein breaking the fluid loss control barrier occurs at least partially concurrently with installing the lower completion.
 28. The on-demand method for making and removing fluid-loss barriers from perforations connecting a wellbore with a formation of claim 17, wherein breaking the fluid loss control barrier happens after installing the lower completion. 